1. Field of the Invention
The present invention relates to micro-structural softening of a workpiece to improve manufacturing process performance.
2. Background Art
Manufacturing processes involve modification of workpieces and assembling workpieces. New high strength alloys are being implemented in manufacturing operations to take advantage of high strength to weight ratio of such materials. There are many advantages relating to the use of high strength alloy materials but manufacturing problems may arise as a result of difficulties encountered when conventional manufacturing techniques are used with such materials.
Certain manufacturing processes may be adversely impacted when applied to high strength materials. For example, the use of self-piercing rivets, attachment of clinch-type fasteners, hydro-forming, and magnetic pulse joining is more difficult when applied to high strength alloys such as heat treatable aluminum, steel, and magnesium alloys. For example, lightweight aluminum self-piercing rivets are not normally useable with high strength alloys because of the hardness of such materials even though their use would allow for weight savings.
High strength materials are generally more brittle than conventional materials and alloys. Brittle materials may crack during manufacturing processes due to limited ductility and may also suffer from material fatigue.
Manufacturing processes such as hydro-forming are limited when applied to high strength materials. For example, aluminum parts may be deformed to a limited extent in hydro-forming. However, high strength alloys can be deformed to a lesser degree of deformation than annealed alloys.
Another manufacturing process is magnetic pulse welding or joining wherein a magnetic pulse is directed between two parts to join the parts together that may be made of dissimilar materials. The use of high strength alloys in one or both of the materials may make it more difficult or limit the use of magnetic pulse welding in certain manufacturing operations.
The above problems and other problems that are apparent to one or more skilled in the art are addressed by applicant's invention as summarized below.